Issues of energy independence, global warming, the reduction of greenhouse gas emissions, especially CO2, the reduction of dependence on fossil fuels as a source of energy and even issues of national security have recently melded into a desire to focus energy generation on renewable resources. In particular, wind, solar thermal and solar photovoltaic technologies have been seen to positively affect all of these issues. The present invention is directed to the construction, installation and use of solar photovoltaic systems and it is these systems that are predominantly described herein. However, those skilled in the solar energy arts also realize that the ideas described herein are also applicable to solar thermal systems as well, although the advantages to be gained are not generally regarded as being as great as those for solar photovoltaic systems.
Given the need and desire to deploy solar energy collection systems, especially solar photovoltaic systems, it is known that certain obstacles exist. One of the most significant of these obstacles is the need to render the “footprint” of such systems as small as possible. Another need in the solar photovoltaic arts is to provide installations which are minimally affected by wind conditions. As should be appreciated, greater reductions in cost are obtained by having as much solar photovoltaic cell area present on a given mast or support structure. However, the larger the solar photovoltaic array, the greater is the horizontal load generated by local wind conditions. Accordingly, support structures for solar photovoltaic systems should be able to withstand local wind conditions. These wind conditions are often exacerbated by the desire to mount solar photovoltaic arrays at heights which might be needed to avoid shading factors from local trees, buildings, terrain based structures or other shade generating entities. Furthermore, the need to design for high wind loads adds to the overall cost of the system by requiring heavier duty construction elements.
It is also noted that there are two basic mounting systems for solar photovoltaic arrays. One of these systems is the so-called roof mount. These systems tend to be fixed, that is, once installed, they are not orientable. As is also known, being able to orient a solar photovoltaic array provides significant advantages in terms of efficiency. Those skilled in the meteorological and geoscience arts fully appreciate the fact that earthly seasons are generated in opposite fashions in the northern as opposed to the southern hemisphere because of the incidence angle of sunlight, thus clearly demonstrating the desirability of angling solar photovoltaic arrays so that they point directly to the sun. Unfortunately for such fixed systems, the sun moves from east to west during the day and from more nearly overhead positions during the summer to more nearly horizontally positions during the winter. It is noted, however, that the summer to winter transitions occur in an annual as opposed to a diurnal cycle; that is, these latter variations occur over a much longer period of time. These variations in solar position make fixed systems significantly less efficient. Accordingly, it would be desirable to have an inexpensive solar photovoltaic installation which tracks the sun in both horizontal and vertical directions.
Roof mounting of solar panels, as opposed to post-mounted systems, exhibit several problems that militate against their use. Firstly, a roof may be oriented in a direction that does not allow significant southern exposure (northern exposure in the southern hemisphere). The roof may also be tilted poorly with respect to light capture. The roof may also be too small to accommodate the desired number or weight of solar panels. The roof may also be lacking in structural strength sufficient to accommodate the desired solar panel weight. Additionally, roof mounting not only makes panel maintenance difficult but also potentially unsafe. Roof maintenance or replacement is also made more complicated and often involves removal and reinstallation of the solar panels. It should also be noted that photovoltaic systems are sensitive to thermal conditions in that higher substrate temperatures lead to lower energy output. In this respect then, it is seen that post-mounted systems exhibit advantages in that they generally have more exposed surfaces for easier cooling.
This is not, however, the whole story. It is noted that even if one were to provide a tracking system which, on a daily basis, simply rotated a solar photovoltaic array about an axis perpendicular to the ground, this would still be less than 100% efficient since the sun courses through an arc well above the horizon. Such a tracking system is ideal only if the sun were to track along the horizon, which it clearly does not. Thus, even on a daily basis, dual axis tracking for solar photovoltaic arrays is seen to be desirable. However, systems for tracking are expensive, often adding from about $4,000.00 to about $7,000.00 to the cost of each post-mounted array, with the lower number being more likely to be able to only purchase a single-axis tracking system. This represents a significant fixed cost that leads many otherwise interested parties to eschew solar photovoltaic systems. In other words, the cost of entry becomes too high for many. This is especially true since many of these systems are installed under financing arrangements whose long term financing schemes add a multiplying factor to each dollar that is needed for an installation.
From the above, it is seen that fixed solar photovoltaic systems have limitations. Since roof mounted systems tend to be fixed in orientation, unless they can be provided with some form of orientable mounting structure, it is seen that ground mounted post-support systems have an advantage. With respect to ground mounted systems, it is seen that the typical installation begins with the establishment and pouring of a concrete foundation or footing. The cost of concrete, site preparation and cleanup are significant elements in the overall cost of the system and, as pointed out above, provides yet another adoption avoidance factor that deters the construction of new installations. Additionally, the use of a concrete (or cement) base adds to the time it takes to install a new solar photovoltaic system. Such structures require one crew to dig the foundation, another possible crew to pour the concrete and a third crew to place the post and solar photovoltaic array in place. This installation modality is thus seen to be not only labor intensive and thus costly, it is also seen to take time while the concrete is cured to a point where it is capable of supporting the mast and the array.
In summary then, it is seen that desirable solar energy systems should employ easily and quickly installable pole structures that provide wind protection, shade avoiding capabilities and the opportunity to easily include single or dual axis tracking capabilities. From the above, it is therefore seen that there exists a need in the art to overcome the deficiencies and limitations described herein and above.